120605 - BE.342/442 Tuesday, December 6, 2005 Topic:...

BE.342/442 Tuesday, December 6, 2005 Topic: Research in Biomaterials Administrative Take-home midterms will be returned on Thursday. Evaluation forms will be filled out today. The last 2 lectures will be dedicated to graduate student presentations. Term papers (grads) or review articles (undergrads) are due December 23 rd as a hard copy delivered to Prof. Zhang’s office in person or by interdepartmental mail. Research groups involved in biomaterials : Google these people—they’ll give you great ideas for research, and for your final projects! Michael Hecht , Princeton University – graduated from MIT in 1985, and now works on combinatorial protein design, selection, and evolution. With over 10 130 possible sequences for a protein of 100 residues, how can we select proteins for desired properties? Many large proteins form into a globular shape in solution, so that the hydrophobic groups can aggregate in the center. The middle position in the 3-nucleic-acid codons has high correlation to the amino acid identity (whereas the third position is usually involved in wobble). This allows a single mutation at the second position to change the encoded amino acid. Michael Hecht designed alpha helices with amino acid sequences that follow a pattern in the primary structre: polar, nonpolar, p, p, n, n, p, p, n, p, p, n, n, p. This virtually guarantees self-assembly into a coiled-coil structure. Hecht incorporated 6 polar residues (Glu, Gln, Asp, Asn, Lys, or His) and 5 nonpolar residues (Met, Leu, Ile, Val, or Phe) and selected 50 of the 5x10 41 possible proteins that display solubility, alpha-helical character, stability to unfolding, cooperative thermal denaturation, and high charge in enthalpy. The protein design considered structure and function, including: globular folded structures, fibers (amyloid structures in nature, or biomaterials), and binding/activity. For example, proteins were selected for their ability to bind air, pattern on surfaces, etc. Reza Ghadiri

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